There have been known many bleaching compositions containing alkali metal hypochlorites as a main component. These compositions are widely used to remove stains, particularly mildew stains, on a hard surface of a bathroom, a bathtub, a kitchen, a drain, and the like. Such a bleaching composition is applied to various hard surfaces including a vertical and an inclined planes in addition to a horizontal plane, and thus required to have retention properties to a target stain in order to exhibit good bleaching performance in any case of being applied to any surface. To satisfy the requirement, many methods for improving retention properties of a bleaching composition have been attempted. For example, JP-A 2003-41300 discloses a detergent product having increased retention properties by providing viscosity to a composition. JP-A 2003-253297 discloses a detergent and a detergent product, that detergent has thixotropic nature and relatively high viscosity, and adheres and uniformly covers the surface of a cleaning target even when it has a net structure without passing through the net by being sprayed in the form of foam having adequate roughness with a sprayer, and thereby the detergent can exhibit good retention properties. JP-A 7-305099 discloses a bleaching composition containing a specific polymer and having good storage stability.
Recently, there are increasing cases of mold growing on resin parts such as silicone resin caulking parts and soft poly(vinyl chloride) resin packing parts used in a joint between a wall and a bathtub and the like in addition to tiles and joints. Although conventional chlorine-based bleaching detergents exhibits sufficient effects on stains of tile and joint and other dark stains, these have not so good bleaching detergency to mildew stains generated on these resin parts. There is thus a need for a bleaching composition having excellent bleaching detergency to mildew stains on resin parts. To meet the need, many methods for increasing bleaching performance to mildew stains on resin parts are studied. JP-A 2002-241791 and JP-A 2002-256289 disclose liquid bleaching detergent compositions containing quaternary ammonium surfactants.